A ferromagnetic body means a material that is spontaneously magnetized even though a strong magnetic field is not applied thereto from the outside. In a magnetic tunnel junction structure (first magnetic body/insulator/second magnetic body) in which an insulator is interposed between two ferromagnetic bodies, an electric resistance varies depending on relative magnetization directions of two magnetic layers, i.e., a tunnel magnetoresistance effect occurs. The tunnel magnetoresistance effect occurs because up-spin and down-spin electrons flow at different degrees at the magnetic tunnel junction structure while tunneling an insulator.
According to the law of action and reaction that is Newton's third law of motion, if the magnetization direction may control a flow of current, it is also possible to control a magnetization direction of the magnetic layer by applying current due to the reaction. If current is applied to the magnetic tunnel junction structure in a direction perpendicular to a film surface, the current spin-polarized by a first magnetic body (fixed magnetic layer) transfers its spin angular momentum while passing through a second magnetic body (free magnetic layer). A torque felt by magnetization due to the transfer of spin angular momentum is called a spin transfer torque. It is possible to fabricate a device for reversing the free magnetic layer or continuously rotating the free magnetic layer using the spin transfer torque or a device for moving a magnetic domain wall of the free magnetic layer using the spin transfer torque.
Moreover, the magnetic tunnel junction may lead to magnetization reversal of a free magnetic layer or movement of a magnetic domain by using a spin-orbit spin torque generated by in-plane current flowing in a conducting wire adjacent to the free magnetic layer.
A magnetization reversal device using a spin-orbit spin torque is disclosed in U.S. Pat. No. 8,416,618 B2.
FIG. 1 is a cross-sectional view illustrating a structure of a magnetic tunnel junction using a spin-orbit spin torque according to a prior art.
Referring to FIG. 1, a magnetic tunnel junction device 10 includes a spin Hall material layer 11 and a magnetic tunnel junction connected to the spin Hall material layer 11. The magnetic tunnel junction includes a fixed magnetic layer 14, a tunnel insulating layer 13, and a free magnetic layer 12 which are sequentially stacked. The free magnetic layer 12 receives spin current from the spin Hall material layer 11 to perform magnetization reversal.